Expendable offset blanket for rotary offset printing machines



1951 Y J. H. GRUVER 2,563,646

EXPENDABLE OFFSET BLANKET FOR ROTARY OFFSET PRINTING MACHINES Filed July1, 1946 r INVENTOR.

da/yw M 6?? v5? BY Zawwwk ATTORNEYS Patented Aug. 7, 1951 UNITED STATESPATENT OFFICE EXPENDABLE OFFSET BLANKET FOR R- TARY OFFSET PRINTINGMACHINES 6 Claims.

The present invention pertains to printing machines and especially toplanographic printing machines of the offset type. It has to do moreparticularly with blankets or coverings for the offset printing membersof such machines, and especially of rotary planographic offset machines.

A machine of the general character to which the present invention isparticularly applicable is described in the patent to Curtis No.2,165,231, although it will be understood that the invention isapplicable to various types of machines of the general types mentionedin the preceding paragraph.

As known in the prior art of which the aforesaid patent to Curtis isexemplary, a planegraphic oifset machine may be so constructed andarranged as to be suitable for use in business offices where there is ademand for printing of good quality at very low cost and with a minimumof equipment. Machines of this character have been widely accepted forsuch work and are commonly used for printing business papers such asletters, bills, orders, invoices and the like in small quantities, whichwould not be economically possible with heavier printing equipment ofolder types.

In many respects the practice of printing very small quantities or veryshort runs of material of the character just mentioned is entirelysatisfactory but in the prior art such practice is open to the veryserious objection that the offset member, which receives an inked imageor imprint from a plate or master, must be cleaned before printing canbe done from a new plate or master. In machines of the characterdescribed in the aforesaid Curtis patent, the cleaning of the oifsetmember, usually a rubber blanket mounted on a revolving cylinder ordrum, is not particularly difficult, but it does consume some time whichprevents rapid and economical production in very short runs. Forexample, as much time is required for cleaning the offset blanket afterprinting two or three or a dozen copies as is required after printing athousand or five thousand. For very short runs the time consumed incleaning may approach or even exceed all other costs of printing, eventhough very efficient cleaning materials are now available. It isfrequently desirable to print as few as a dozen or even fewer copies,where, forexample, a sufficient number cannot be produced on atypewriter, or where carbon copies are objectionable, paper stock tooheavy, or a particular quality of work is required. (30mmsitions usedfor cleaning are commonly somewhat toxic in character and repeated andfrequent use is likely to be injurious to those who operate the machine.For this additional reason it is desirable to reduce the cleaningrequirements in machines of the aforesaid character.

Therefore it is an object of my invention to avoid the necessity ofcleaning the offset blanket, after very short runs, by using anexpendable offset blanket.

A further object of my invention is to employ as an expendable offsetblanket a translucent sheet which may also serve as a copy or record ofthe matter printed.

A still further object is to insure accurate printing of detail vbyemploying a continuous sheet as an offset blanket so that each printingis applied and transferred only once. 7

Another object is to utilize a continuous transparent or translucentnon-absorbent sheet as a protective cover for the normal offset blanket,such sheet bearing an image or imprint which is legible through thesheet notwithstanding the fact that the image or imprint applied to theface thereof is in reverse.

Still a further object is to combine a novel offset blanket withelements of a planographic printing machine in a new and useful manner.

An additional object is to eliminate the danger of injury to operatingpersonnel by reason of the toxic properties of cleaning compounds bymaking it unnecessary to clean the offset cylinder or blanket aftershort runs.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawing which, by way of illustration, shows a preferredembodiment of the present invention and the principle thereof and what Inow consider to be the best mode in which I have contemplated applyingthat principle. Other embodiments of the invention embodying the same orequivalent principles may be used and structural changes may be made asdesired by those skilled in the art without departing from the presentinvention and the purview of the appended claims.

In the drawing the single figure shows a longitudinal vertical sectionalView of. a planographic offset printing machine embodying my invention.

The machine shown in the drawing corresponds in most respects with thatshown and described in the aforesaid patent to Curtis No.

- 2,165,331 and reference may be had to such patent for constructiondetails which are unnecessary herein to illustrate and describe theinstant invention. Briefly the machine comprises a pair of frame membersseparated and braced by transverse rods I3 and carried by suitablesupporter, legs or frame elements not shown.

A plate cylinder l5 carries a pl'anographic plate I! which can bereadily attached or detached by securing means l9 and 2|. A shaft 23supports the cylinder l5 in the side frames The plate I! is inked by aform roller 25 which receives ink from a transfer roller 21. The roller2'! receives ink from a ductor roll 29 which is supported for periodicmovement between roller 2'! and a fountain roller 3| which is mounted inan ink fountain 33 and provided with a blade or wiper 35. The printingplate H is moistened, as well known in the art, by means comprising aform roller 4|, ductor roller 113,

and fountain roller 45 which is mounted in a fountain '41 containing asuitable moistening composition 'which is effective to render nonimagebearing portions o'f plate-H ink-repellant.

The planographic plate ll normally is effective to transfer or imprintthe inked image carried thereby to the surface of a rubberor like offsetblanket 5| which in turn applies the image thus received to a sheet. Theblanket 5| is mounted on an offset cylinder or drum 53 supported .on ashaft '55 suitably journaled in side frames H. 'Tension'ing means 51 and59 hold the blanket .in place.

The blanket 5! is normally-effectiveto receive a transferred.imprintfrom plate H, as indicated above, and to transfer itto sheets or thelike S which are pressed against such blanket by a platen roller 6|.This roller is carried by .pivoted arms '63 which are urged upwardly bya spring 65, such'movemen't being limited by an adjustable screw memberBl.

Sheet feedingmechanism may be provided, including a magazine TH, a sheetbuckling member 13 and .an advancing roller F5, or, if desired,

Isheets may be fed manually, as is well known in the art.

In order to avoid'the necessity of cleaning the V offset cylinder 53 orthe blanket 5| carried there- The sheetB is .passed around the offsetcylinder "53 so that it covers the normal offset blanket 5| and is .thenled between the oifset roller 53 and the. platen roller 6| where it ispressed into contact with sheets S which are to be printed. In

the drawing two such sheets S1 and S2 are shown already printed andother sheets S3 and S4 are in position to be fed sequentially to theprinting mechanism.

Inasmuch as the expendable paper sheet B is to serve as an offsetblanket for a limited number of printing operations and is intended tomake it unnecessary to clean the normal blanket 5|, the paper materialmust be properly selected.

lt'must be receptive to ink imprinted thereon by the plate cylinder,must retain the image without loss of detail as it moves to position toprint the sheets S, and then must release enough ink to form a goodimpression on the printed sheet. A non-absorptive paper having a smoothsurface, for example a vellum paper or an enamel surfaced pa-perha-sbeen foimd to be satisfactory.

By using a transparent or translucent paper the expendable blanket B maybe read from the reverse side and instead of being discarded afterprinting, it .may be out into sheets which will serve as additional orrecord copies of the printed matter. Hence the paper blanket B need notbe discarded even though the image printed on its face is in reverse.

For some purposes the sheet B may be of a length merely sufficient tocover the normal blanket 5| and may be secured to the cylinder 53 by theattaching means 51, 59 or by other suitable attaching means, not shown.In this case 'thepaper sheet B servesias a'tem'p'orary blanket in thesame manner asthe regular blanket "51. It of course is not suitable 'forverylon'g runs and cannot be cleaned, but if it is anon-absorbentmaterial having a smooth surface of proper texture for icking up andtransferring ink, printing may be accomplished substantially withoutloss of detail. The "blanket "B "in this case is replaced each time'thepl'anograp'hic plate is changed. The blanket removed maybedi'scarded, or if it is of transparent ortran'slucent imaterial, 'itmay befreta'ined asa'n'add'itional or record copy of "the printing.

When the continuous blanket'ior "sheet B is used, as shown'in'thedrawing, it'is'preferably of a length equivalentto'th'eperipheralmeasure of .theroller 53 'm'ultiplie'dby the number of"sheets S to beprinted. The advance end of the sheet B is fed betweenthe plate roller and the oifset roller and returned above the sheetfeeder and platen roller and above the printed sheets as S1 and S2.

While sheets S are being printed,*thecontin- 'u'ous sheet B is beingadvanced. The machine material it is possible to secure'rapid andeconomical production involving very short runs. Where the consumptionof paper blanket material is objectionable, it may be preferred tofasten .it to the offset cylinder, as described above, but normally thearrangement illustrated in the drawing is preferred for very short runs.

While I have referred to paper as being the preferred material, it willbe understood that cellophane, glassine, and the like may be suit ablefor some types of operation and it is'intended to cover the use ofalternatematerials so far as permitted by the prior art.

Hence, while I have illustrated and described the preferred embodimentsof my invention, it is to be understood thatthese are capable ofvariation and modification and I therefore do not wish to be limited tothe precise details set forth, but desire to availmyself of such changesand alterations as fall within the purview of the following claims.

I claim:

1. In an offset printing machine, the combination of a cylindrical platecarrying member adapted to have a planographic printing plate mountedthereon, inking and moistening means for such a plate, a cylindricaloifset member, a platen cooperating with said offset member, means forcyclically rotating said printing member and said offset member, and astrip of nonabsorbent paper of substantially greater length than thecircumference of said offset printing member and extended about asubstantial portion of the offset member for movement therewith andadapted to be fed through and out of the machine as an incident to themovement thereof with said offset member whereby an unused portionthereof ispresented to said printing member in each cycle of operationso that the printing image on said plate is transferred to said paperstrip and from the strip to a sheet of paper passed between the offsetmember and the platen in each cycle of operation.

2. In an offset printing machine, the combination of a planographicprinting cylinder, an off= set cylinder, means for cyclically rotatingsuch cylinders, and an offset blanket of translucent paper ofsubstantially greater length than the circumference of the offsetcylinder and extended about a substantial portion of the periphery ofsaid offset cylinder and serving as a printed record of mattertransferred from said printing cylinder thereonto in reverse, saidelongated blanket being fed through the machine to thereby constantlypresent an unused portion thereof on the periphery of the offsetcylinder, said trans lucent paper enabling the reverse printed record onone face thereof to be read directly from the other face thereof.

3. In a planographic printing machine, the combination of a planographprinting member, inking and moistening means for said member, an offsetprinting member comprising a normal blanket and an expendable blanketextended about a substantial portion of the periphery of said normalblanket for movement therewith and to receive and transfer ink forlimited runs, said expendable blanket comprising a sheet ofsubstantially non-absorbent paper.

4. In a planographic printing machine, the combination of a planographicprinting cylinder,

inking and moistening means for said cylinder, an offset printingcylinder including a normal offset blanket, and a continuous expendableoffset blanket of paper substantially non-absorbent to ink and extendedabout a substantial portion of the periphery of said offset printingcylinder to serve as a covering for said normal blanket and effective toserve as a printed record of matter transferred from said planographiccylinder.

5. In a planographic printing machine, the combination of an offsetprinting cylinder, a normal offset blanket secured to said cylinder andsuitable for long runs, and an expendable paper blanket covering asubstantial portion of the periphery of said normal blanket for shortruns and effective to receive and transfer i-- prints from a printingmember to a limited number of articles, thereby rendering unnecessarythe cleaning of said normal blanket.

6. The combination which comprises an offset printing cylinder, a normaloffset blanket se cured to said cylinder and suitable for long runs, anda continuous expendable paper blanket extended about a substantialportion of the periph= ery of said normal blanket to cover said normalblanket for short runs and to receive and transfer imprints from aprinting member to a number of articles proportional to the length ofsaid continuous blanket, thereby rendering unnecessary the cleaning ofsaid normal blanket.

JOHN H. GRUVER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 420,765 Brings Feb. 4, 1890427,318 Hawkins May 6, 1890 719,324 Goss Jan. 2'7, 1903 829,193 BarrettAug. 21, 1906 938,043 Dean Oct. 26, 1909 1,976,039 Rowell 'Oct. 9, 19341,989,375 Meyercord Jan. 29, 1935 2,163,958 Neidich June 27, 19392,165,231 Curtis July 11, 1939 OTHER REFERENCES Hacklemans CommercialEngraving and. Printing, 1921, Commercial Engraving Pub. Co.,Indianapolis, Indiana, page 320.

